Using database mirroring system events to send notification email when failover occurs

Use MirrorServerDisconnect and the MirrorFailover events as a mechanism to send notification via email that action may be
required on the mirror database. These events may not fire in all situations that result in the database running on the primary
server becoming unavailable. For example, a power outage affecting both the primary and mirror servers would prevent either
of these events from being fired. If this type of monitoring is required, it can be implemented on a separate computer via
a scripting language by calling dbping to periodically connect to the mirror database.